The finer points of Divinity: Original Sin II's skill system might not be immediately clear to those completely new to the series or to those who expect skills to work in exactly the same way as they did in the first Original Sin game. And this is where this PC Gamer's build guide comes into play. It describes every skill tree in the game and lists some of their signature skills, as well as the possible synergies to be had if you combine them. Now, you are of course still encouraged to experiment with skill combinations yourself, especially considering that starting from Act 2 you can respec at will, but this guide is a nice starting point that covers the basics. A snip:

A point or two in Warfare will help out anyone who deals physical damage, which mostly happens through weaponry. The related skills center around melee combat and shields, though, so while it's useful for archers, high Warfare levels are best for tanky brawlers. You'll get skills such as Battle Stomp, which knocks down opponents, and Phoenix Dive, which lets you leap into battle and create a fire surface beneath you. High level abilities such as Guardian Angel, which reflects 50% of nearby allied damage to you, expect you to be heavily armored.

If you want to whack things in the head, but also use magic, Warfare pairs fine with any other ability—hence why it's included in four class presets.

For a warrior-healer Paladin type, Hydrosophist is a good pairing. With Warfare and Hydrosophist, you can focus on equipping physical armor, and use water spells to buff your magic armor when needed. You'll also be able to heal vitality, and freeze enemies for crowd control. The abilities Cleanse Wounds and Mass Cleanse Wounds, which restore vitality and remove many negative statuses, require points in both Warfare and Hydrosophist.

The Inquisitor preset pairs Warfare with Necromancer. Necromancer abilities deal physical damage, making Warfare immediately useful. The morbid arts also include healing abilities and a physical armor buff. Plus, tanky Necromancers can use Shackles of Pain to deal all damage they take to a target, and Last Rites to sacrifice themselves by taking damage to resurrect a target character. Buff Necromancers get the job done.

Another good pairing, Polymorph, includes several abilities that require you to get in close, as well as one that regenerates physical armor, so it works well with strong sword and shield characters. Its skills also deal physical damage, which Warfare boosts, and some rely on Strength, so it'll become more powerful at the same time as your strength-based weapons. And who doesn't want to be a fighter who can turn their hair into snakes?

This is your classic ranger archetype, with skills that center around bow and arrow trick shots and staying the hell away from melee enemies. It includes one close-range healing ability, First Aid, arrow attacks such as Pin Down, a crippling shot, and Reactive Shot, which works like overwatch in XCOM, letting you take shots at moving enemies between turns. Two points in Huntsman is the prerequisite for a skill that's useful for any ranged character, Tactical Retreat, which applies haste and teleports you out of harm's way.

If you're dropping points into Huntsman, you must be an archer, so you'll benefit from other ranged abilities. The two existing preset classes make for good combos. Wayfarer pairs Huntsman with Geomancer, giving you abilities such as Fossil Strike, which creates an oil puddle that slows enemies and can be lit with fire arrows. If you have points in both Huntsman and Geomancer, you can also learn Throw Dust, which blinds enemies. The Ranger class preset instead pairs Huntsman with Pyrokinetic for some ranged fire spells, as well as the ability to toss out explosive traps if you've put points into both.

If someone else in your party has Aeurotheurge, they can learn Teleportation (there's also a certain set of gloves that grants this ability) which is useful for getting ranged characters to high ground (unlike Tactical Retreat, it can't be used on yourself which is why it's best to equip a non-archer with it).